234 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1956 



sides. The dark, round spots, which Lowell believed to be cities, oases 

 in the desert, were seen by Mellish as craters, presumably of volcanic 

 origin, and also filled with water. 



We have three opinions about these mysterious canals. The first 

 regards them as ditches dug by the Martians and indicative of an 

 advanced civilization, the work of superhuman intelligences. The 

 second does not attempt to decide whether they are natural or arti- 

 ficial, but denies that they are continuous features, declaring them 

 to be series of isolated and apparently quite separate spots. The third 

 regards them as natural features, in fact cracks in the surface and 

 therefore natural waterways. 



The regular appearances of the isolated dark spots, Lowell's cities, 

 were also to some extent broken down into collections of separate dots 

 with the Meudon telescope. On the other hand, Mellish regards them 

 as craters, and therefore regular. That there is life of some sort 

 on Mars is now generally admitted, but the question to be answered 

 is whether this consists merely of vegetation, possibly with some 

 elementary animal life, or whether there exist on Mars today, or 

 have existed in the past, creatures somewhat resembling man, beings 

 capable of reasoning and of constructing civil engineering projects 

 on a scale far exceeding anything which man has achieved on the 

 earth. 



This question of whether we have brothers in the sky, or at any 

 rate on Mars, is of the utmost importance. If there are intelligent 

 beings on Mars it is not impossible that they may seek to communicate 

 with us, or even to leave their drying-up planet and migrate to our 

 pleasantly watered and warmer world. Is it possible for highly 

 organized beings to exist on Mars ? 



We already know that the diameter of Mars is 4,200 miles, to which 

 we can add that this globe is not as closely packed as the earth, the 

 density being 3.94 times that of water, while the figure for the earth 

 is 5.52. The small diameter and the low density mean that the 

 mass of Mars, the amount of matter in it, is only slightly more than 

 one-tenth of that of the earth. The surface of Mars, or its area, is 

 not quite three-tenths and the intensity of gravity at its surface is 

 not quite four-tenths (more precisely 0.38) that of our globe. 



The low surface gravity is just about sufficient to allow the planet 

 to retain an atmosphere composed of oxygen and nitrogen, with some 

 water vapor. The red color and the spectroscopic evidence that there 

 is little free oxygen in the atmosphere mean that much of the free 

 oxygen the atmosphere probably once possessed has entered into com- 

 bination with the surface rocks. The amount of water vapor is limited, 

 but still sufficient for the formation of polar caps and occasional 

 morning mists and clouds. The true water-vapor clouds can be dis- 

 tinguished from what appear to be dust or sand storms by their 



